This laboratory has studied the molecular basis of embryogenesis in Xenopus laevis and the zebrafish, with special emphasis on axis determination and pattern formation. These events are thought to be controlled by cell-to-cell signaling and by the spatially and temporally regulated action of transcription factors. The Xlim-1 gene encodes a LIM-homeodomain protein that has been shown to be involved in the functions of the Spemann organizer in neural induction and mesoderm patterning. This gene is also important in kidney formation. The function of Xlim-1 is being studied by application of an oligonucleotide antisense strategy. Modified antisense oligonucleotides that are stable in the embryo have proven valuable tools for the analysis of Xlim-1 function during gastrulation. A screen for developmentally regulated genes is being conducted in zebrafish. By screening for genes with restricted expression patterns, valuable information is collected about gene control of embryogenesis. The mbx gene has been studied in zebrafish development. It encodes a homeodomain protein that has a role in eye development. in another study, the role of the FGF, Wnt, and retinoic acid signaling pathways in the patterning of the zebrafish nervous system has been studied. All three pathways are involved in specification of the posterior nervous system. Mechanisms regulating the FGF pathway have been studied further, and regulatory molecule including a protein phosphatase and a novel inhibitory factor named Sef have been characterized.